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Omega-3 fatty acid

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**Sources of Omega-3 Fatty Acids**:
– ALA is found in plants, while DHA and EPA are found in algae and fish.
– Common plant oil sources of ALA include walnuts, flaxseeds, and hempseed oil.
– Sources of EPA and DHA include fish, fish oils, and algae oil.
– Marine algae and phytoplankton are primary sources of omega−3 fatty acids.
– Mammals need to obtain ALA through diet and can convert it to EPA and DHA.

**Health Benefits and History**:
– Omega−3 fatty acids play a crucial role in human physiology.
– Aging may impair the ability to convert ALA to longer-chain omega−3 fatty acids.
– Interest in essential fatty acids grew since the 1980s.
– FDA granted qualified health claim status to EPA and DHA in 2004.
– Evidence on omega−3 supplementation reducing cancer or cardiovascular disease risk is inconclusive.

**Chemistry and Nomenclature**:
– Omega−3 fatty acids have multiple double bonds, with the first between the third and fourth carbon atoms.
– ALA, EPA, and DHA are key omega−3 fatty acids in human physiology.
– Omega−3 fatty acids are named based on the location of the double bond.
– The IUPAC recommends using n to identify the highest carbon number.
– The nomenclature system helps understand the structure of unsaturated fatty acids.

**Mechanism of Action and Interconversion**:
– Essential fatty acids are crucial for normal growth in young children and animals.
– Humans convert short-chain omega−3 fatty acids to long-chain forms (EPA, DHA) with less than 5% efficiency.
– ALA and DHA values in women’s plasma phospholipids may be influenced by delta-6-desaturase.
– Enzymes in sheep tissues convert omega−6 arachidonic acid into inflammatory agents.
– Omega−6 and omega−3 fatty acids compete for synthesis, affecting growth and health.

**Dietary Recommendations, Contamination, and Supplements**:
Fish like herring, salmon, mackerel, and tuna are rich in omega−3.
– The Institute of Medicine sets RDAs and AMDRs for nutrients like α-linolenic acid.
– Heavy metal poisoning from consuming fish oil supplements is unlikely due to selective binding with fish flesh proteins.
Fish oils that are molecularly distilled under vacuum are of the highest grade.
– Omega-3 supplements do not show significant benefits for mortality or cardiovascular health.

Omega-3 fatty acid (Wikipedia)

Omega−3 fatty acids, also called Omega−3 oils, ω−3 fatty acids or n−3 fatty acids, are polyunsaturated fatty acids (PUFAs) characterized by the presence of a double bond, three atoms away from the terminal methyl group in their chemical structure. They are widely distributed in nature, being important constituents of animal lipid metabolism, and they play an important role in the human diet and in human physiology. The three types of omega−3 fatty acids involved in human physiology are α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). ALA can be found in plants, while DHA and EPA are found in algae and fish. Marine algae and phytoplankton are primary sources of omega−3 fatty acids. DHA and EPA accumulate in fish that eat these algae. Common sources of plant oils containing ALA include walnuts, edible seeds, and flaxseeds as well as hempseed oil, while sources of EPA and DHA include fish and fish oils, and algae oil.

Mammals are unable to synthesize the essential omega−3 fatty acid ALA and can only obtain it through diet. However, they can use ALA, when available, to form EPA and DHA, by creating additional double bonds along its carbon chain (desaturation) and extending it (elongation). Namely, ALA (18 carbons and 3 double bonds) is used to make EPA (20 carbons and 5 double bonds), which is then used to make DHA (22 carbons and 6 double bonds). The ability to make the longer-chain omega−3 fatty acids from ALA may be impaired in aging. In foods exposed to air, unsaturated fatty acids are vulnerable to oxidation and rancidity.

There is no high-quality evidence that dietary supplementation with omega−3 fatty acids reduces the risk of cancer or cardiovascular disease. Fish oil supplement studies have failed to support claims of preventing heart attacks or strokes or any vascular disease outcomes.

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